US5305330A - System comprising a laser diode and means for stabilizing the wavelength of light emitted by said laser diode, and laser interferometer - Google Patents

System comprising a laser diode and means for stabilizing the wavelength of light emitted by said laser diode, and laser interferometer Download PDF

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Publication number
US5305330A
US5305330A US08/039,959 US3995993A US5305330A US 5305330 A US5305330 A US 5305330A US 3995993 A US3995993 A US 3995993A US 5305330 A US5305330 A US 5305330A
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wavelength
set forth
light
beams
photodetector
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US08/039,959
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English (en)
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Heinz Rieder
Max Schwaiger
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RSF Elektronik GmbH
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RSF Elektronik GmbH
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Assigned to RSF-ELEKTRONIK GESELLSCHAFT M.B.H. reassignment RSF-ELEKTRONIK GESELLSCHAFT M.B.H. ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: RIEDER, HEINZ, SCHWAIGER, MAX
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
    • H01S5/068—Stabilisation of laser output parameters
    • H01S5/0683—Stabilisation of laser output parameters by monitoring the optical output parameters
    • H01S5/0687—Stabilising the frequency of the laser

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  • This invention relates to a system comprising a laser diode and means for stabilizing the wavelength of a primary beam of light emitted by said laser diode, wherein said means comprise a controller for controlling the current supplied to the laser diode under the control of sensor means, which are responsive to the instantaneous ambient conditions and operating parameters, a beam splitter, which is disposed in the path of said primary beam and arranged to divert from said primary beam a partial beam to measuring means, which comprise photodetector means, which are illuminated by said partial beam via optical means with an intensity that varies in dependence on the wavelength of said primary beam, which photodetector means are operable to deliver output signals, which are optionally converted and are delivered as control signals to said controller.
  • said means comprise a controller for controlling the current supplied to the laser diode under the control of sensor means, which are responsive to the instantaneous ambient conditions and operating parameters, a beam splitter, which is disposed in the path of said primary beam and arranged to divert from said primary beam a partial beam
  • This invention relates also to a laser interferometer which comprises a system as defined in the preceding paragraph, a second beam splitter for splitting said primary beam into a reference beam directed to a stationary reflector and a measuring beam, which is directed to a movable reflector that is adapted to be connected to a movable object, and reflecting means for diverting the reflected beams to photodetector means, which are connected to counters for detecting the fluctuations of the brightness resulting from the interference of the reflected beams during a movement of the movable reflector.
  • DE-A-39 11 473 discloses stabilizing means of the kind described hereinbefore in conjunction with the laser diode of a laser interferometer.
  • the light emitted by the laser diode is split into a plurality of partial beams, the length of which is transmitted by respective monomode optical fibers.
  • One of said fibers leads to a lens, from which the measuring light beam is directed along the measuring path.
  • a second fiber transmits reference light to a receiver, and the measuring light beam is diverted by an adjustable measuring prism and is transmitted by a lens and the light of the measuring beam is subsequently transmitted by a further fiber to said receiver and in said receiver is caused to interact with said reference beam with interference.
  • light of two further beams is diverted and is transmitted by optical fibers of equal length to an additional interference generator to interact therein with interference.
  • the exit openings of said optical fibers are arranged one beside the other so that the projected light beams can interfere and in the photodiodes spaced from the exit openings generate electric signals having an intensity that varies in dependence on the wavelength.
  • a constant distance between the light exit openings and the photodetectors must be maintained for the measurement and for the stabilization of the wavelength.
  • a solid-state laser which is stimulated by at least one laser diode and converts the light emitted by the laser diode in the infrared range to light of a different wavelength.
  • That solid-state laser consists, e.g., of a neodymium solid-state laser and can be used to stabilize the beam and the wavelength.
  • a separate measuring interferometer is used, which receives a partial light beam, which has been diverted from the measuring beam. Any changes of the wavelength will result in the measuring interferometer in corresponding bright-dark changes, which can be utilized for an automatic control. That automatic control results either in a change of the current supplied to the stimulating laser diode or in a change of the control of the resonator surfaces of the solid-state laser.
  • the accuracy of the measurement of length by an interferometer will depend on the fact that the wavelength of the laser light employed is known and is maintained constant.
  • the number of bright-dark changes is counted which in case of an adjustment of the movable reflector result from the interference between the reference beam and the measuring beam.
  • ⁇ 1 m ⁇ /2, wherein ⁇ 1 is the change of the path length, m is the number of bright-dark changes, and ⁇ is the wavelength of the laser.
  • the intensity of the light which is received by the photodetectors varies according to a sine function.
  • the resolution may be increased by the use of suitable circuits.
  • interferometers comprise stable sources of laser light, such as Zeeman-stabilized He-Ne lasers.
  • the air parameters are detected individually or by means of so-called wavelength trackers are detected jointly. If stabilized sources of laser light are employed, the frequency and, as a result, the wavelength cannot be changed and cannot be automatically controlled by usable control means but each result of the measurement must be corrected in computers with suitable correcting data.
  • the frequency of laser diodes can often change in dependence on various operating parameters and such changes may often be undesirable.
  • the frequency may also change in dependence on the ageing of the laser diode.
  • a use of the means known in conjunction with stabilized lasers for a correction of the result of measurement would be too expensive and would not give sufficiently accurate results. For this reason it has been attempted in the operation of laser diodes to stabilize the wavelength by a control of the current supplied to the laser diode. In that case the ambient conditions and operating parameters are detected by separate sensor means and a feedback loop for controlling the current supplied to the laser diode is operated in response to said sensor means.
  • a second object of the invention is to provide a laser interferometer in which the wavelength is stabilized by a system provided to accomplish the first object and which permits an improved evaluation of the results of the measurement and a higher resolution to be achieved by the use of simple final evaluating means.
  • the measuring means comprise a diffraction grating with or without focusing optical means for focusing the deflected partial beam so that the position and/or size of the area occupied by a light spot which is formed by said optical means on photodetector means will depend on the instantaneous wavelength of the primary beam and the photodetector means will detect any deviation of the light spot from the desired area, which is associated with a rated wavelength of said primary beam.
  • the position and/or area of the light spot (focal spot) formed by the partial beam which has been diffracted and focused will depend on the wavelength in the transmitting medium and in case of proper measurements said wavelength will correspond to the wavelength in the path used for the measurement.
  • the focusing which is effected results in a high selectivity so that even slight deviations of the wavelength can be used to generate appropriate control signals, i.e., for a feedback control, and the wavelength can actually be stabilized within very close limits.
  • Various structural designs may be employed within the scope of the invention.
  • the light spot is focused during an operation at the rated wavelength on a gap between two photodetectors consisting particularly of photodiodes and is shifted to one photodiode in response to an increase of the wavelength and to the other photodiode in response to a decrease of the wavelength so that the output signal of the photodetectors will represent the instantaneous deviation.
  • Such a system is very simple and permits the output signal of the photodetectors to be used directly for the control of the current supplied to the laser diode.
  • the diffraction grating consists of an echelette grating, i.e., of a grating having grating elements which are sawtooth-shaped in a longitudinal sectional view.
  • the diffraction grating is a self-focusing concave grating. In that case it is not necessary to provide separate optical means for focusing.
  • the laser diode is powered via an analog adder, which has inputs connected to a constant-current source and via an integrator to an amplifier for amplifying the current from the photodiodes; said analog adder generates a sum current and supplies said sum current to the laser diode.
  • the photodiodes may be connected in opposition so that the analog adder may increase and decrease the current relative to the rated current delivered by the constant-current source.
  • the integrator may constitute a low-pass filter in order to avoid a hunting in the automatic control.
  • the second beam splitter is a polarizing beam splitter for polarizing the primary beam in a plane which includes an angle of 45° with the reference beam, which is normal to the measuring beam, so that the polarization planes of the reference and measuring beams include an angle of 90°, the polarized reflected beams are directed before or after they are diverted through at least one lambda/4 plate having ordinary and extraordinary axes which include angles of 45° with the polarization planes of the two reflected beams so that two circularly polarized waves are generated, which are combined in a combined beam to produce a resultant wave, which is linearly polarized in a direction which depends on the position of the movable reflector relative to the stationary reflector, and is rotated about the axis of said combined beam in response to an adjustment of the movable reflector, and said combined beam is divided by a neutral beam split
  • either of the signal trains will lead the other in dependence on the direction in which the movable reflector has been adjusted so that the measuring signal trains which have been generated will definitely indicate also the direction in which the movable reflector has been adjusted.
  • Countable binary signals may be derived from the signal trains and be delivered to conventional counting circuits, which are known in connection with incremental measuring systems. Even the resolution can be increased by means of multiplier circuits or interpolating computers, known per se. But the essential advantage resides in the fact that conventional evaluating means may be used in an only slightly modified form.
  • the laser interferometer defined hereinbefore is similar to the design of the standard laser interferometer in that the reference beam is diverted from the primary beam at right angles to the latter and the measuring beam is projected in the same direction as the primary beam. Other designs may be adopted, in which the light is deflected through different angles and in that case the inclination of the plane of the polarization of the primary beam and the positions of the reflectors and beam splitters will have to be modified accordingly.
  • the second beam splitter constitutes the reflecting means for diverting the reflected beams and at least one lambda/4 plate is arranged in the paths for said diverted beams.
  • a common lambda/4 plate or two separate lambda/4 plates may be arranged in the paths for the two diverted beams.
  • FIG. 1 is a highly schematic top plan view and a block scheme showing a laser interferometer in accordance with an illustrative embodiment of the invention.
  • FIG. 2 shows means for focusing the partial beam on two photodetectors in order to explain the mode of operation of the stabilizing system.
  • FIG. 3 is a block circuit diagram of the means for energizing the laser diode.
  • a single-frequency laser interferometer with the exception of the movable reflector are mounted on a common baseplate 1, which is made of a material that has a very low coefficient of expansion, e.g., of invar.
  • a laser diode 2 emits a divergent light bundle 3, which is collimated by a lens 4, which projects a primary beam 5 of polarized light.
  • the laser diode 2 is so adjusted that the light of the primary beam 5 is polarized in a plane which is inclined 45° from the horizontal and from the direction in which light is projected by a beam splitter, which will be described hereinafter.
  • Said means comprise a beam splitter 6, by which a partial beam 7 is diverted from the primary beam 5 and is directed to a phase grating 8, by which the partial beam is diffracted and which projects light 9 in a direction which depends on the wavelength.
  • the diffracted light passes through a positive lens 10 or other converging optical means and is focused thereby. If the frequency of the laser diode 2 corresponds to the rated wavelength, the waist of the focused beam portion 11 will be disposed in the gap 12 between two photodiodes 13, 14. In response to a change of the wavelength, the light spot will be shifted by a distance ##EQU1## wherein f is the focal length of the lens 10
  • ⁇ is the wavelength change
  • ⁇ is the diffraction angle
  • the two diodes 13, 14 may alternatively consist of a twin diode and a differential signal derived from their output signals is processed further in an evaluating circuit 15, which is shown in FIG. 3 to comprise a current-to-voltage converter 16, a preamplifier 17, and an integrator 18 as well as a voltage-to-current converter 19. Owing to the provision of an operational amplifier the integrator serves also as a low-pass filter.
  • the output signal of the evaluating circuit 15 is delivered to a power source 20 for the laser diode 2.
  • said power source comprises a constant-current source 22 and a controller consisting of an analog adder 21.
  • the output signals from 15 are used to modulate the constant current from source 22 in order to change the current value of the energizing current supplied to the laser diode in such a manner that the focal spot or the waist of the focused light bundle 11 will be held in the gap 12 because the frequency is adapted to the instantaneous ambient conditions and operating parameters and the wavelength is thus maintained constant.
  • the laser diode 2 is provided with a Peltier cooler 23. Even the slightest changes of the position of the focal spot will result in a strong signal. On the other hand, changes of the intensity of the partial beam 7 will produce only slight results, if any. If the diffraction grating 8 is made of a material having a very small coefficient of expansion, the diffraction angle will also be independent of temperature. In a practical example the gap 12 had a width of 5 micrometers and the focal spot 20 was 20 micrometers in diameter.
  • the primary beam 5 is polarized in a plane which is inclined from the horizontal by 45°.
  • the primary beam 5 is split by a polarizing beam-splitting cube 24 into a measuring beam 25, which is aligned with the primary beam 5, and a reference beam 26, which has been deflected at right angles. Because a polarizing beam splitter is used, the two beams 25 and 26 are polarized in planes which are at right angles to each other.
  • the beam 26 After traversing a predetermined reference path the beam 26 is incident on a stationary triple reflector 27 and the beam 25 is incident on a movable triple reflector 28, which is firmly connected to and can be adjusted in unison with the movable part of the interferometer, such as a measuring carriage 29.
  • the reflected beams which have been reflected by 27 and 28 are combined in the beam splitter 24 and are diverted at right angles by a mirror or a reflecting prism 30.
  • the two diverted beams are jointly designated 31. Because they have different polarizations, they cannot yet interact to produce interference. For this reason they are transmitted by a lambda/4 plate, which has ordinary and extraordinary axes which include angles of 45° with the polarization planes of the two partial beams; said planes are at right angles to each other.
  • the diverted beams 31 which have been transmitted by the plate 32 are combined in a combined beam 33 and constitute two waves, which have mutually opposite circular polarizations and which are combined in the combined beam 33 to form a resultant wave having linear polarization.
  • the vector of the direction of the polarization will depend on the position of the movable reflector 28 relative to the stationary reflector 27 and in response to an adjustment of the movable reflector will be rotated about the axis of the combined beam 33 in a sense which depends on the direction of the adjustment.
  • a neutral beam splitter 34 the combined beam 33 is then split into two partial beams 35, 36, which are directed to respective polarizing beam-splitting cubes 37, 38.
  • Said beam-splitting cubes 37, 38 are inclined 45° relative to each other so that the four light beams 39, 40, 41 and 42 projected by them are polarized in planes at angles of 0°, 90°, 45° and 135°, respectively.
  • the intensity of said light beams will depend on the angle of the polarization of the light that has been projected by the lambda/4 plate 32 and will change with the rotation of that polarization so that an adjustment of the measuring carriage 29 will have the result that pairs of sinusoidal signals displaced 90° in phase relative to each other will be generated by the photodetectors 43, 44, 45, 46 and will be delivered to evaluating means 47.
  • said evaluating means 47 the pairs of signals are processed in phase opposition in antiparallel circuits to provide two measured-value signals, which are displaced 90° in phase and from which all d.c. components have been eliminated by the antiparallel circuit.
  • said measured-value signals are converted to countable digital signals, which are delivered to indicating or control means 48.
  • the diffraction grating 8 may consist of an echelette grating.
  • the diffraction grating 8 and the optical means 10 may be replaced by a concavely curved, focusing diffraction grating.
  • the reflected beams may already be diverted by the correspondingly designed beam-splitting cube 24.
  • the common lambda/4 plate 32 may be replaced by two lambda/4 plates, which are disposed in the light paths 25, 26, respectively, for the reflected beams before the beam-splitting cube 24.

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  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Optics & Photonics (AREA)
  • Instruments For Measurement Of Length By Optical Means (AREA)
  • Spectrometry And Color Measurement (AREA)
US08/039,959 1992-04-02 1993-03-30 System comprising a laser diode and means for stabilizing the wavelength of light emitted by said laser diode, and laser interferometer Expired - Fee Related US5305330A (en)

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AT0067792A AT396841B (de) 1992-04-02 1992-04-02 Anordnung zur stabilisierung der wellenlänge des von einer laserdiode abgegebenen lichtstrahlesund laser-interferometer
AT677/92 1992-04-02

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Cited By (33)

* Cited by examiner, † Cited by third party
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US5420687A (en) * 1993-10-04 1995-05-30 Science Solutions Inc. Interferometer with processor for linearizing fringers for determining the wavelength of laser light
ES2079282A2 (es) * 1993-09-13 1996-01-01 Fagor S Coop Ltda Dispositivo interferometrico y metodo para medir y para estabilizar la longitud de onda de diodo laser.
US5483342A (en) * 1993-06-25 1996-01-09 Hughes Aircraft Company Polarization rotator with frequency shifting phase conjugate mirror and simplified interferometric output coupler
US5495332A (en) * 1994-08-30 1996-02-27 Alliedsignal Inc. Arrangement for sensing the wavelength shift of light from a polychromatic light source
US5543916A (en) * 1993-10-04 1996-08-06 Science Solutions, Inc. Interferometer with alignment assembly and with processor for linearizing fringes for determining the wavelength of laser light
US5565987A (en) * 1995-03-23 1996-10-15 Anvik Corporation Fabry-Perot probe profilometer having feedback loop to maintain resonance
US6201820B1 (en) * 1997-03-05 2001-03-13 Silkroad, Inc. Optically modulated laser beam transceiver
DE19940981C1 (de) * 1999-08-28 2001-07-12 Bruker Optik Gmbh Fourier-Transform-Infrarot-Spektrometer und Interferometer
US6275516B1 (en) * 1998-07-02 2001-08-14 Agere Systems Optoelectronics Guardian Corp. Article for detecting power drift in the putout of a diode array source
US20010036206A1 (en) * 1999-09-20 2001-11-01 Jerman John H. Tunable laser with microactuator
US6331892B1 (en) 1998-10-16 2001-12-18 New Focus, Inc. Interferometer for monitoring wavelength in an optical beam
US6434173B1 (en) 1998-09-11 2002-08-13 New Focus, Inc. Open loop wavelength control system for a tunable laser
US20020125405A1 (en) * 2000-10-18 2002-09-12 Tsai John C. Light wavelength meter
US20020172239A1 (en) * 1999-07-27 2002-11-21 Mcdonald Mark E. Tunable external cavity laser
US20030007522A1 (en) * 2001-07-06 2003-01-09 Hua Li External cavity laser with orthogonal tuning of laser wavelength and cavity optical path length
US20030016707A1 (en) * 2000-07-27 2003-01-23 Mcdonald Mark Wavelength reference apparatus and method
US20030063290A1 (en) * 2001-10-01 2003-04-03 Kathman Alan D. Non-etalon wavelength locking optical sub-assembly and assoicated methods
US6639679B2 (en) 2000-01-10 2003-10-28 Telefonaktiebolaget L M Ericsson (Publ) Integrated wavelength monitor
US6658031B2 (en) 2001-07-06 2003-12-02 Intel Corporation Laser apparatus with active thermal tuning of external cavity
US6687008B1 (en) 2000-10-19 2004-02-03 Kla-Tencor Corporation Waveguide based parallel multi-phaseshift interferometry for high speed metrology, optical inspection, and non-contact sensing
US6718092B2 (en) * 2001-09-14 2004-04-06 Fibera, Inc. Frequency detection, tuning and stabilization system
US6724797B2 (en) 2001-07-06 2004-04-20 Intel Corporation External cavity laser with selective thermal control
US6795459B2 (en) 2000-10-18 2004-09-21 Fibera, Inc. Light frequency locker
US6804060B1 (en) 2001-09-28 2004-10-12 Fibera, Inc. Interference filter fabrication
US6804278B2 (en) 2001-07-06 2004-10-12 Intel Corporation Evaluation and adjustment of laser losses according to voltage across gain medium
US6822979B2 (en) 2001-07-06 2004-11-23 Intel Corporation External cavity laser with continuous tuning of grid generator
US6856632B1 (en) 1999-09-20 2005-02-15 Iolon, Inc. Widely tunable laser
US6879619B1 (en) 1999-07-27 2005-04-12 Intel Corporation Method and apparatus for filtering an optical beam
US7209498B1 (en) 2000-05-04 2007-04-24 Intel Corporation Method and apparatus for tuning a laser
US7230959B2 (en) 2002-02-22 2007-06-12 Intel Corporation Tunable laser with magnetically coupled filter
US20100278201A1 (en) * 2007-08-10 2010-11-04 Connector Optics Limited Wavelength division multiplexing system
US20160261084A1 (en) * 2015-03-06 2016-09-08 3Dfamily Technology Co., Ltd. Real-time wavelength correction system for visible light
FR3090099A1 (fr) * 2018-12-18 2020-06-19 Université de Technologie de Troyes Dispositif laser pour interferometrie a polarisation

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Cited By (52)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5483342A (en) * 1993-06-25 1996-01-09 Hughes Aircraft Company Polarization rotator with frequency shifting phase conjugate mirror and simplified interferometric output coupler
ES2079282A2 (es) * 1993-09-13 1996-01-01 Fagor S Coop Ltda Dispositivo interferometrico y metodo para medir y para estabilizar la longitud de onda de diodo laser.
US5420687A (en) * 1993-10-04 1995-05-30 Science Solutions Inc. Interferometer with processor for linearizing fringers for determining the wavelength of laser light
US5543916A (en) * 1993-10-04 1996-08-06 Science Solutions, Inc. Interferometer with alignment assembly and with processor for linearizing fringes for determining the wavelength of laser light
US5495332A (en) * 1994-08-30 1996-02-27 Alliedsignal Inc. Arrangement for sensing the wavelength shift of light from a polychromatic light source
US5565987A (en) * 1995-03-23 1996-10-15 Anvik Corporation Fabry-Perot probe profilometer having feedback loop to maintain resonance
US6201820B1 (en) * 1997-03-05 2001-03-13 Silkroad, Inc. Optically modulated laser beam transceiver
US6275516B1 (en) * 1998-07-02 2001-08-14 Agere Systems Optoelectronics Guardian Corp. Article for detecting power drift in the putout of a diode array source
US6614829B1 (en) 1998-09-11 2003-09-02 New Focus, Inc. Mechanically grounded tunable laser
US6434173B1 (en) 1998-09-11 2002-08-13 New Focus, Inc. Open loop wavelength control system for a tunable laser
US6493365B1 (en) 1998-09-11 2002-12-10 New Focus, Inc. Passive thermal stabilization of the optical path length in a tunable laser
US6331892B1 (en) 1998-10-16 2001-12-18 New Focus, Inc. Interferometer for monitoring wavelength in an optical beam
US6853654B2 (en) 1999-07-27 2005-02-08 Intel Corporation Tunable external cavity laser
US6879619B1 (en) 1999-07-27 2005-04-12 Intel Corporation Method and apparatus for filtering an optical beam
US20020172239A1 (en) * 1999-07-27 2002-11-21 Mcdonald Mark E. Tunable external cavity laser
US6888856B2 (en) 1999-07-27 2005-05-03 Intel Corporation Method and apparatus for filtering an optical beam
DE19940981C1 (de) * 1999-08-28 2001-07-12 Bruker Optik Gmbh Fourier-Transform-Infrarot-Spektrometer und Interferometer
US7443891B1 (en) 1999-09-20 2008-10-28 Coherent, Inc. Widely tunable laser
US6847661B2 (en) 1999-09-20 2005-01-25 Iolon, Inc. Tunable laser with microactuator
US20080259972A1 (en) * 1999-09-20 2008-10-23 Iolon, Inc. Widely tunable laser
US6856632B1 (en) 1999-09-20 2005-02-15 Iolon, Inc. Widely tunable laser
US20010036206A1 (en) * 1999-09-20 2001-11-01 Jerman John H. Tunable laser with microactuator
US6639679B2 (en) 2000-01-10 2003-10-28 Telefonaktiebolaget L M Ericsson (Publ) Integrated wavelength monitor
US7209498B1 (en) 2000-05-04 2007-04-24 Intel Corporation Method and apparatus for tuning a laser
US7120176B2 (en) 2000-07-27 2006-10-10 Intel Corporation Wavelength reference apparatus and method
US20030016707A1 (en) * 2000-07-27 2003-01-23 Mcdonald Mark Wavelength reference apparatus and method
US20020125405A1 (en) * 2000-10-18 2002-09-12 Tsai John C. Light wavelength meter
US6795459B2 (en) 2000-10-18 2004-09-21 Fibera, Inc. Light frequency locker
US6858834B2 (en) 2000-10-18 2005-02-22 Fibera, Inc. Light wavelength meter
US6687008B1 (en) 2000-10-19 2004-02-03 Kla-Tencor Corporation Waveguide based parallel multi-phaseshift interferometry for high speed metrology, optical inspection, and non-contact sensing
US6724797B2 (en) 2001-07-06 2004-04-20 Intel Corporation External cavity laser with selective thermal control
US20030007522A1 (en) * 2001-07-06 2003-01-09 Hua Li External cavity laser with orthogonal tuning of laser wavelength and cavity optical path length
US6804278B2 (en) 2001-07-06 2004-10-12 Intel Corporation Evaluation and adjustment of laser losses according to voltage across gain medium
US20050078717A1 (en) * 2001-07-06 2005-04-14 Intel Corporation Laser apparatus with active thermal tuning of external cavity
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EP0564431A1 (de) 1993-10-06
ATA67792A (de) 1993-04-15
AT396841B (de) 1993-12-27
DE59300075D1 (de) 1995-03-16
EP0564431B1 (de) 1995-02-01

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